In microsurgery such as ophthalmological surgery, small, precision, mechanical structures with ultra-sharp edges are needed. In addition, many shapes and cutting edge variations such as serrated knives and interocular saws are needed for specialized surgery in the region of the eye. Further, it is important that these instruments be made of a mechanically stable material that is both hard and durable.
Conventionally, these edged medical tools are either mass produced from metals such as tungsten, or hand ground from harder materials such as diamond, silicon and sapphire. The disposable metal knives are relatively blunt and wear quickly over time. The nondisposable diamond knives, on the other hand, are expensive and brittle. Further, current techniques of fabricating these harder knives are unable to produce certain cutting edge variations such as serrations that are needed in this type of surgery. Accordingly, there is a substantial need for both edged tools free from the above mentioned problems and ways to make edged tools in a less expensive manner.
Japanese Patent Kokai No. 63-92345 suggests an edged medical tool wherein the surface of the edge tool is provided with a carbonaceous coating layer of a diamond-like crystalline structure having a thickness of 1 to 20 nm which is deposited by the plasma-induced vapor-phase deposition in an atmosphere of a gaseous mixture of hydrogen and a hydrocarbon compound such as methane.
U.S. Pat. No. 4,980,021 to Kitamura et al. suggests the step of etching the diamond-like coating layer formed in a process such as that of the foregoing Kokai with a plasma of hydrogen gas to such an extent that the surface of the edged tool has a roughness of 0.5 to 5 nm. Although this improves the incisiveness of the edged tool, the process starts with an existing base body that was already shaped and, therefore, does not enable the fabrication of knives with serrations and other cutting variations that are needed in opthalmological surgery.
Microelectronic fabrication techniques have been developed in the field of semiconductors. U.S. Pat. No. 4,916,002 to Carver discloses a microminiature tip assembly which is fabricated using photolithography and anisotropic etching. The crystalline form of silicon is taken advantage of by etching along the grain boundaries to form a pit in an silicon substrate. Tungsten is then deposited into the pit to form a sharp tip for use as a scanning tunneling microscope.
Another microfabrication technique disclosed in U.S. Pat. No. 4,740,410 to Muller is a method of producing a micromechanical structure with two or more members measuring less than 1000 micrometers in any linear dimension. The patent technique provides sacrificial layers of material that are later etched away so that the mechanical members become movable relative to each other. Neither of the foregoing, however, addresses the above mentioned problems in the field of microsurgical instruments.
U.S. Pat. No. 4,551,192 to DiMillia et al. discloses the use of a silicon carbide body in a pinchuck formed with microcircuit lithography and U.S. Pat. No. 4,911,782 to Brown discloses a miniature biological chamber made with photolithography, but neither concern cutting instruments.
In view of the foregoing, an object of the present invention is to provide a relatively inexpensive way to mass produce microsurgical knives from a variety of different materials.
Another object of the present invention is to provide a means by which a variety of different microsurgical knives may be produced simultaneously as a single batch.
Still another object of the present invention is to provide microsurgical instruments having a scraper surface.
A further object of the present invention is to provide microsurgical knives in a variety of new and unique shapes, such as serrated knives and concavely shaped knives.